Continuously operated compressors



Nov. 19, 1963 P. P. DEMAY coNTrNuousLY OPERATED coMPREssoRs 3 Sheets-Sheet 1 Filed March 22. 1961 INVENTOR.

PETER P. DEMAY 5%?, ATT /VEY Nov.'19, 1963 P. P. DEMAY coNTmuousLY OPERATEDv coMPREsoRs 3 Sheets-Sheet 2 Filed March 22. 1961 INVENToR.

PETER P. DEMAY f@ Arro Ey Nov. 19, 1963 P. P. DEMAY 3,111,259

CONTINUOUSLY OPERATED C O MPRESSORS Filed March 22. 1961 3 Sheets-Sheet 3 INVENTOR.

PETER P. DEMAY ,arr /vEy United States Patent O 3,111,259 CGNTlNUUSLY GERATED CMPRESSRS Peter P. Bernay, Chicago, lll., assignor to Minneapolis- Honeytvell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed Mar. 22, 1961, Ser. No. 97,575 12 Claims. (Cl. 230-58) My invention relates to compressors and more particularly to a small, low-cost, continuously operating compressor suitable for use as a pneumatic supply and control source in the operation of individual pneumatic controls used in small installations such as residential heating and Ventilating systems and in similar commerical installations.

Air compressors of this type are known and used. The operating requirements for continuous operation of devices of this type present certain maintenance problems, particularly as to the filters included in the compressor, and because of wear to the moving parts particularly to bearings in eccentrically driven piston type compressors. The present apparatus is directed to an improved compressor design which permits simple maintenance of the air filter and providing ter sizing for adequate inlet air. In addition it provides an eccentric drive to the movable piston of the compressor with provision for oscillating the cylinder and manifold connected thereto to take up side thrust and bearing wear due to the oscillatory motion imparted to the piston by the eccentric drive. Therefore, it is an object of this invention to provide an improved, small, low cost, continuously operated type of air compressor suitable for supplying a pneumatic control source to operate individual controllers in residential and small commercial type pneumatic installations. Another object of this invention is to provide in a compressor of this type an arrangement in which a bracket within a casing mounts the drive motor, transmission, manifold and cylinder for the compressor with an air inlet in a removable portion of the casing and a filter included in the air inlet. A still further object of this invention is to provide a piston type compressor which is mounted on a journalled manifold to take up side thrust and wear in the eccentric driving connection between the piston and the driving means. These and other objects of the invention will be apparent from a reading of the attached description together with the drawings wherein:

FIGURE l is a side elevation view of my improved compressor with parts in section,

FIGURE 2 is a sectional View of the compressor of FIGURE 1 taken along the lines 2--2 of FIGURE l,

FIGURE 3 is a sectional View of the compressor shown in FIGURE 2 taken along the line 3-3 therein, and

FIGURE 4 is a sectional view of another embodiment of the compressor.

My improved compressor is shown in the drawings as housed in a casing generally indicated at lll, the casing being generally boxlike or rectangular in form and having a removable front cover portion or member 11 which is adapted to be suitably secured to the casing through a screw means such as indicated at 12. As indicated in FIGURES 2 and 3 t .e casing also includes a back cover 14 which is mounted on or otherwise suitably secured to the side portions of the casing and permits assembly of the apparatus that is normally not removable. The casing is designed to be substantially airtight and includes an aperture in the front cover indicated at 15 which, as will be later noted, provides the air inlet to the compressor. Positioned in this aperture is a filter indicated at 2t) having a suitable screen portion 21 positioned on either side of the same to hold the filter in position and provide for air passage therethrough.

As will best be seen in FIGURES 2 and 3, there is po- 3',l l i259 Patented Nov. 19, 1963 ice sitioned within the casing a dividing wall or support 25 which extends between the sides of the casing and as will be later noted serves to mount the components of the compressor. Although the divider or support is shown integral with the casing walls herein, it will be recognized that this may be a separate part which is secured to the casing walls. Mounted on this Wall or support is plate 26 which mounts the drive motor 28. Motor 28 is secured to plate Z6 through connecting means 2? extending through an aperture (not shown) in the supporting wall. The plate in turn is adjustably connected to the wall Z5 through nuts and bolts Sil, as will be later noted. The operating shaft 31 extends through an aperture in the supporting wall (not shown) and mounts a pinion member 33 which is positioned on the opposite side of the wall from the motor.

Also positioned on this side of the support 25 within the casing and mounted in line with the pinion 33 is a pulley il? which is mounted on a shaft 41 and suitably secured thereto through a key means indicated at 42. The shaft is journalled in a flange portion 45 on the support member 25 through suitable bearing inserts, indicated at do, the shaft extending to the opposite side of the support member from that on which the pulley is located. A belt 5@ is positioned around the pulley and pinion in a driving connection such that rotation of the motor may be imparted through the pulley to the shaft in a conventional manner. Motor mounting plate 26 is adjustable to provide proper tension on belt 56.

Support member 25 also mounts a manifold 55 for the pump or compressor, the manifold having a pair of bearing or journalled surfaces or trunnions at either extremity thereof as indicated at 56 which t into a bearing insert 57 in the support wall and a bearing insert 58 positioned in an aperture in the cover 11 to support the manifold and pivot the same between these tWo structures (see FIGURE 3). The manifold 55 includes an axially extending port or passage oil having a tapped outer extremity 61 which forms the outlet for the compressor and extends beyond the face or the cover portion 11 of the casing. The manifold also includes a transversely extending port or passage o5 from the outlet passage which is positioned intermediate the trunnion surfaces 56 of the manifold and provides a relief passage terminating in a relief valve indicated at 66 in FIGURE 2. The relief valve is conventional and is housed in a hub portion 67 on the manifold. It includes a valve seat 68 and a valve closure member o? cooperating therewith which is urged against the seat by means of a spring 70. The spring 70 is held in position and guided by means of a guide member 71 threaded into a tapped aperture in the flange 67 and including an adjusting screw 72 bearing against the extremity of the spring to adjust the tension on the same. A transversely extending passage 73 communicating with the interior of the casing and the chamber between the valve closure member and the spring guide 71 provides an outlet path beyond the check valve.

The manifold 55 'also includes ange portions 75, 7 by means of which the manifold mounts the cylinder indicated generally at vfor the pump. Included in this `assembly of parts is an outlet check valve section, indicated at 81, which is held is assembled relationship with cylinder 8() and manifold 55 'by means of screw means indicated fat 84. Communicating with the outlet port or passage 69 is a transversely extending passage 85 extending through the `check valve section S1 in which a valve seat 86 is incorporated. A valve closure member 87 guided in a guide section S9 of manifold 55 `cooperates with the valve seat to provide the valving in the passage from the compressor to the outlet port 69. The valve closure member has associated therewith a spring 8S which urges the closure member down on the valve seat, and the valve able screw means indicated at 175. These trunnion blocks mount and journal the manifold which is shown in its modified form at 180. Manifold 180 includes a pair of earing surfaces 131, 132 which rest in or ride in a pair of split sleeve type bearings 183, 184 in block 171, 172. It will be seen in the drawing that the upper halves of the split bearings are secured or positioned by keys 155 and hence prevented from rotating, and that the lower halves are engaged by a thrust plate 186 of a biasing spring 137 which includes a screw 183 bearing against free extremity of the spring to load the lower half of the bearing and hence the journalling of the manifold in the trunnion blocks.

In this embodiment the cylinder or casing 189 isagain attached to the manifold through suitable means (not shown) and is sealed thereto by means of an 0 ring sealing member 190. The casing 189 includes the aperture or opening 192 through which the eccentric 164 and the shaft 165 extend. In addition, casing 189 includes a small inlet air opening 194 through which inlet air enters to the cylinder. Piston member 195 is somewhat diterent in coniiguration from that of the before mentioned embodiment and defines with the end of the cylinder the compression chamber 196 into which air is directed from the passage 194. The outlet passage from the compression chamber indicated at 199 includes the Valve seat 2% for the outlet check valve. Cooperating with the valve seat is a valve closure member 201 and a cooperating biasing spring 202 which is carried in a plug member 2133 threaded into a tapped aperture 294 in the manifold which forms part of a passage leading to an outlet conduit 265. This check valve is conventional and in this embodiment the relief check valve is omitted for simplicity, it being understood that it can be included or omitted as desired. The relief valve, if included in the manifold, would, as in FIGURE 2, be positioned in a transversely extending passage to the main outlet passage or port 265 of the device.

Thus, air enters the compression chamber 196 through the passage 194 as distinguished in the rst mentioned embodiment in a passage included Within the piston. Movement of the piston within the chamber or casing 189 above the port 194 will close the inlet air valVing to the compression chamber allowing the air above the piston to be compressed and released as controlled by the check valve 299, 2&1. This arrangement simplifies the inlet Valving as well as the details of the piston. The driving shaft 165 of the piston is located in a recess 210 of the piston in which are positioned the split bearing 211, the upper half of which is keyed as at 212 and the lower half of which includes the bias plate 214 and spring 216 to take up wear and load the bearing surface. The spring and plate 214, 216 are held in position by means of a bolt member 218 threaded into a tapped aperture in the piston. In addition, the piston is sufliciently recessed as at 220 to allow for movement of the eccentric within the piston and the cylinder. At the top of the piston 195 or adjacent the compression chamber is a plastic or cornposite sealing ring 225 which replaces the conventional split sealing ring shown in the aforementioned embodiment. This plastic sealing ring made up of integral multiple rectangular sections of non-elastic material is slightly deformable and is held in position on the piston by means of an end cap or support 230 connected to the piston through a suitable screw means 231. Backing up the plastic sealing member is a wedge-shaped ring 232 and a spring 234 which wedges the ring against the inner periphery of the sealing member 225 forcing it out against the cylinder walls to provide an airtight seal therebetween. This arrangement permits takeup of wear in the sealing member and assures proper seal of the compression chamber.

The lower extremity of the piston includes a conventional 0 ring or plastic seal member 246 held in position by means of a support ring 244 which in turn is secured to 6 a piston by means of a connecting and spring adjusting member 218 or bolt which in turn is held or secured from rotation by means of a lockwasher indicated at 245. This lower end of the piston is primarily guided or journalled within the cylinder by the ring member 240 which prevents wear of the piston at this point.

Although not shown, it will be understood that the casing surrounding the bracket, the manifold and motor, cylinder and piston mounted thereon will include the air filter, the electrical connector to the motor and the outlet port. In this embodiment, a stationary connector bracket projects through the casing, such as is indicated at 250, the connector bracket having a tapped aperture 251 therein into which the outlet connections or piping to the device to be actuated is directed. The block 255i includes a recess 252 which houses a spring 254 and backing plate 255 for a cone type plastic seal member 260 which member ts against the extension or journal surface of one half of the manifold concentric with the output passage 265. rlhe opposite peripheral extremity of the member 26d bears against the surface of the block 250 in the cupshaped recess 252 to provide a seal for air coming from the passage 205 and directed to the output port 251. The block 25@ is connected to the trunnion block 171 through suitable means, such as metal bolts 265, and is sealed therein by means of gasket material 265. The casing includes an aperture through which this stationary block member 25? extends to provide for access to the tapped outlet port 251 from without the casing.

This embodiment of the :compressor operates substantially in the manner of that described in connection with FIGURES 1, 2 and 3. One of the changes incorporated is a direct connection of the motor to the shaft of the compressor. In addition, the manifold 186` is journalled in separate trunnion `blocks connected to the flange or support for the compressor, with the bearings being split and biased to provide for wear takeup at this point. Similarly, the piston is so journalled on the output shaft with spring loading on a split bearing to take up wear at this point. The upper end of the cylinder in this embodiment includes a special compression seal in the form of a deformable plastic ring which is continually biased by means of a wedge ring against the cylinder walls -msuring a positive seal and wear compensation. This embodiment of the invention also eliminates the special valving and filtering within the piston and relies on piston position for controlling the opening or closing of a passage in the Wall of the cylinder which permits the iiow of inlet air to the compression chamber 196. The details of the output check valve are conventional and special sealing is provided -between a stationary part and the movable manifold to permit connection at the cover to a stationary part of the device.

As indicated above, much of the parts directly similar to the aforementioned embodiment are omitted herein, such as the air filter and the enclosing casing. As in the aforementioned embodiment, air is directed through the removable filter in the casing cover portion to the interior of the casing and the inlet to the cylinder. Energization of the motor through the connector located on the casing will cause rmotor rotation and will drive the eccentric to oscillare the piston within the cylinder. Wear takeup in this embodiment as mentioned above is permitted in the special journalling of the manifold.

In considering this invention it should be remembered that the present disclosure is intended to be illustrative only and the scope of the invention should be determined only by the appended claims.

I claim as my invention:

l. In a compressor, a casing, a support included `within said casing, a motor and a pulley mounted on said support within said casing, driving means connected between said motor and pulley for transmitting rotation of said motor to said pulley, a manifold section including a pair of cylindrical trunnions mounted on said support within said casing, a thin walled cylinder having an aperture therein secured to said manifold section and adapted to be pivoted therewith on said trunnions, a piston having a journal slideably positioned within said cylinder, an eccentric shaft means connected to said pulley and extending through said aperture in the wall of said cylinder being journaled in said piston, a passage in said piston connecting with the aperture in the wall of said cylinder and to a compression chamber formed between said piston and said cylinder, check valve means included in said passage, outlet and relief ports included in said manifold section, a second passage included in part in said cylinder and in part in said manifold section connecting said outlet and said relief ports leading to said compression chamber, outlet check Valve means included in said second passage, a flange on said piston, spring means connected between said cylinder and the flange on said piston and adapted to load said journal connection between said eccentric shaft means and said piston, a removable cover portion on said casing including a second aperture therein, filter means included in said second aperture in said cover portion, means connecting said cover portion to said casing and limiting the flow of air therethrough except through said filter means, a third aperture included in said cover portion, said outlet port cooperating with said third aperture in said cover portion to be accessible from outside of said casing, and electrical terminal means included in said cover portion and connected to said motor.

2. In a compressor, a casing, a support included within said casing, driving means mounted on said support, a manifold including a pair of cylindrical trunnions mounted on said support within said casing, a cylinder secured to said manifold and adapted to be pivoted therewith on said trunnions, a piston slideably positioned within said cylinder, an aperture in said cylinder, eccentric shaft means connected to said driving means and said piston, means included on said shaft means and said piston for journaling said piston, a compression chamber formed Ibetween said piston and said cylinder, an air inlet ow control means controlling flow of air to said compression chamber included in part in said aperture in said cylinder and in part in said piston being controlled by the movement of said piston, an outlet port and a second passage included with said manifold and connected to said compression chamber, outlet check valve means included in said second passage, a removable cover portion on said casing including an air intake opening therein, and lter means included in said air intake opening in said cover portion.

3. In a compressor, a casing, a support included within said casing, a motor mounted on said support within said casing, driving means connected to said motor for transmitting rotation of said motor thereto, a manifold section including a pair of cylindrical trunnions mounted on said support within said casing, a cylinder having a first aperture therein secured to said manifold section and adapted to be pivoted ytherewith on said trunnions, a piston slideably positioned within said cylinder, an eccentric shaft means connected to said driving means and extending through said first aperture in said cylinder being journaled in said piston, a passage in said piston connecting with the aperture in said cylinder and to a compression chamber formed between said piston and said cylinder, check valve means included in said passage, outlet and relief ports included in said manifold section, a second passage leading to said compression chamber, outlet check valve means included in said last named passage, spring means connected between said cylinder and said piston being adapted to load said journaled connection between said eccentric shaft means and said piston, a removable cover portion on said casing including an aper-ture therein, and filter means included in the aperture in said cover portion, said cover portion on said casing limiting the passage of air therethrough except through said filter means.

4. in a compressor, a casing, a support included within said casing, a motor mounted on said support within said casing, driving means connected to said motor for transmitting rotation of said motor thereto, a manifold including a pair of cylindrical trunnions mounted on said support within said casing, a cylinder having an aperture therein secured to said manifold and adapted to be pivoted therewith on said trunnions, a piston slideably positioned within said cylinder, an eccentric shaft means connected to said driving means and extending through the aperture in said cylinder and being journaled in said piston, a compression chamber provided by said pistonfwithin said cylinder, air inlet flow control means included in part in said piston and in part in said cylinder to control How of air to said compression chamber, an outlet passage included in said manifold connected to said compression chamber, outlet check valve means included in part in said last named passage, spring means included with said piston adapted to bias the journaled connection between said eccentric shaft means and said piston, a removable cover portion on said casing including a ltered air inlet aperture therein, exhaust port means connected with said outlet passage and extending through said cover portion, and electrical terminal means included in said cover portion and connected to said motor.

ln a compressor, a casing, a support included within said casing, a motor mounted on said support within said casing, driving means connected to said motor and transmitting rotation of said motor thereto, a manifold including a pair of cylindrical trunnions mounted on said support within said casing, a cylinder having an aperture therein secured to said manifold and adapted to be pivoted therewith on said trunnions, a piston slideably positioned within said cylinder, an eccentric shaft means connected to said driving means and extending through said aperture in said cylinder being journaled in said piston, a passage in said piston connecting with the aperture in said cylinder, a compression chamber formed between said piston and said cylinder, said passage being connected to said compression chamber, check Valve means included in said passage, a second passage in said manifold, outlet and relief ports included in said manifold and connected to said second passage and said compression chamber, outlet and relief check valve means included in said second passage, a removabie cover portion on said casing including an air inlet aperture therein, and filter means included in the air inlet aperture in said cover portion, said cover portion on said casing limiting the flow of air therethrough except through said filter means.

6. In a compressor, a casing, a support included within said casing, driving means mounted on said support, a manifold including a pair of trunnions mounted on said support and said casing, a cylinder having an aperture therein secured to said manifold and adapted to be pivoted therewith on said trunnions, a piston slideably positioned within said cylinder, an eccentric shaft means connected to said driving means and extending through said aperture in said cylinder being journaled in said piston, a rst passage including inlet check valve means in said piston connecting with the aperture in said cylinder, a compression chamber formed between said piston and said cylinder and connected with said first passage inlet check valve means in said first passage, outlet and relief ports included in said manifold, and connected to a second passage in said manifold leading to said compression chamber, outlet check valve means included in said second passage, spring means connected between said cylinder and said piston being adapted to load said journaled connection between said eccentric shaft means and said piston, a removable cover portion on said casing including an air inlet aperture therein, filter means included in the air inlet aperture in said cover portion, said cover portion of said casing limiting the flow of air therethrough except through said filter means, said outlet port extending through said cover portion, and electrical terminal means included in said cover portion and connected to said motor.

7. ln a compressor, a casing, a support included within said casing, driving means mounted on said support, a manifold including a pivot means mounted on support for movement relative thereto, a cylinder having an aperture therein secured to said manifold and adapted to be pivoted therewith, a piston slideably positioned within said cylinder, an eccentric shaft means connected to said driving means and extending through said aperture in said cylinder being journaled in said piston, a iirst passage in said piston connecting with the aperture in said cylinder, a compression chamber formed between said piston and said cylinder, and connected to said tirst passage, inlet check valve means included in said first passage, an outlet port and a second passage included in said manifold and connected to said compression chamber, outlet check valve means and relief valve means included in said second passage, a removable cover portion on said casing including an air inlet aperture therein, and iilter means included in the air inlet aperture in said cover portion, said cover portion on said casing limiting the flow of air therethrough except through said filter means, said outlet port extending throuvh said cover portion of said casing.

8. in a compressor, a casing, a support included witl.- in said casing, driving means mounted on said support, a manifold including pivot means mounted on said support and adapted to pivot relative thereto, a cyli der having an aperture therein secured to said manifold and adapted to be pivoted therewith on said support, a piston slideably positioned within said cylinder, an eccentric shaft means connected to driving means and extending through said aperture in said cylinder being journaled in said piston, a rst passage in said piston connecting with the aperture in said ci linder to a compression chamber formed between said piston and said cylinder, connected to said first passage, inlet check valve means included in said iii-st passage, an outlet port and a second passage included in said manifold and connected to said compression chamber, outlet checlt valve means included in said second passage, a removable cover portion on said casing including a iltered inlet aperture therein, said cover portion on said casing limiting the ilow of air therethrough except through said ltered aperture.

9. In a compressor, a casing, a support included within said casing, a motor mounted on said support, driving means connected to said motor, a manifold including a pair of trunnions mounted on said support in said casing, a cylinder secured to said manifold and adapted to be pivoted therewith on said trunnions, a piston slidea'oly positioned within said cylinder, an eccentric shaft vneans connecting said driving means to said piston, a passage in said cylinder, a compression chamber formed between said piston and said cylinder connected to said passage, inlet valve means include in said passage and controlled by movement or said piston, an outlet passage in said manitold connected to said compression chamber, outlet check valve means included in said outlet passage, a removable cover portion on said casing including an air inlet aperture therein, and lter means included in the air inlet aperture of said cover portion.

l0. In a compressor, a casing, a support included within said casing, a motor mounted on said support, driving means connected to said motor, a manifold lincluding a id cylinder, a compression chamber formed between piston and said cylinder, and connected to said pasinlet valve means included in part in said passage and controlled by the movement of said piston, an outlet assage in said manifold connected to said compression c 'amber and including an outlet check valve means, and

et aperture.

ll. ln a compressor, a casing, a support included within said casing, a motor mounted on said support, driving m rs connected to said motor, a manifold including a pmi of trunnions mounted on said support in said casing, a cylinder secured to said manifold and adapted to be pivoted therewith on said trunnions, a piston slideably position-ed within said cylinder, eccentric shaft means, means connec g said driving means through said shaft to said piston, for operation of said piston, an air et passage said cylinder, a compression chamber iormed between said piston and said cylinder and connected to said inlet passage, inlet valve means included in part said piston and controlled by the movement of said piston, an outlet passage in said manifold connected to said compression chamber and including an outlet check valve means, spring biased bearing means included in with said piston and loading the connection ben aid shaft means and said piston, a removable cover cover portion.

l2. in a compressor, a casing, a support included Within said casing, a motor mounted on said support, driving means connected to said motor, a manifold including a pair o'r` trunnions mounted on said support in said casing, a cylinder secure to said manifold and adapted to be pivoted therewith on said trunnions, a piston slideably po "oned witl said cylinder, a grooved sealing member of non-elastic deformable material mounted on said piston and sealing the sliding engagement of said piston with said cylinder, bias means connected to said piston and positioned within said sealing member to urge and deform it against the wall of said cylinder, eccentric shaft means connecting said driving means to said piston, a passage in said cylinder, a compression chamber formed between said piston and said cylinder, connected to the passage, inlet valve means formed by said passage and piston and controlled by the movement of said piston, an outlet passage in said manifold connected to said compression chamber and including an outlet check valve means, a removable cover portion on said casing including air inlet aperture, and lter means included in said air inlet aperture or" said cover portion.

References Cited in the iile of this patent UNTED STATES PATENTS 

1. IN A COMPRESSOR, A CASING, A SUPPORT INCLUDED WITHIN SAID CASING, A MOTOR AND A PULLEY MOUNTED ON SAID SUPPORT WITHIN SAID CASING, DRIVING MEANS CONNECTED BETWEEN SAID MOTOR AND PULLEY FOR TRANSMITTING ROTATION OF SAID MOTOR TO SAID PULLEY, A MANIFOLD SECTION INCLUDING A PAIR OF CYLINDRICAL TRUNNIONS MOUNTED ON SAID SUPPORT WITHIN SAID CASING, A THIN WALLED CYLINDER HAVING AN APERTURE THEREIN SECURED TO SAID MANIFOLD SECTION AND ADAPTED TO BE PIVOTED THEREWITH ON SAID TRUNNIONS, A PISTON HAVING A JOURNAL SLIDEABLY POSITIONED WITHIN SAID CYLINDER, AN ECCENTRIC SHAFT MEANS CONNECTED TO SAID PULLEY AND EXTENDING THROUGH SAID APERTURE IN THE WALL OF SAID CYLINDER BEING JOURNALED IN SAID PISTON, A PASSAGE IN SAID PISTON CONNECTING WITH THE APERTURE IN THE WALL OF SAID CYLINDER AND TO COMPRESSION CHAMBER FORMED BETWEEN SAID PISTON AND SAID CYLINDER, CHECK VALVE MEANS INCLUDED IN SAID PASSAGE, OUTLET AND RELIEF PORTS INCLUDED IN SAID MANIFOLD SECTION, A SECOND PASSAGE INCLUDED IN PART IN SAID CYLINDER AND IN PART IN SAID MANIFOLD SECTION CONNECTING SAID OUTLET AND SAID RELIEF PORTS LEADING TO SAID COMPRESSION CHAMBER, OUTLET CHECK VALVE MEANS INCLUDED IN SAID SECOND PASSAGE, A FLANGE ON SAID PISTON, SPRING MEANS CONNECTED BETWEEN SAID CYLINDER AND THE FLANGE ON SAID PISTON AND ADAPTED TO LOAD SAID JOURNAL CONNECTION BETWEEN SAID ECCENTRIC SHAFT MEANS AND SAID PISTON, A REMOVABLE COVER PORTION ON SAID CASING INCLUDING A SECOND APERTURE THEREIN, FILTER MEANS INCLUDED IN SAID SECOND APERTURE IN SAID COVER PORTION, MEANS CONNECTING SAID COVER PORTION TO SAID CASING AND LIMITING THE FLOW OF AIR THEREGTHROUGH EXCEPT THROUGH SAID FILTER MEANS, A THIRD APERTURE INCLUDED IN SAID COVER PORTION, SAID OUTLET PORT COOPERATING WITH SAID THIRD APERTURE IN SAID COVER PORTION TO BE ACCESSIBLE FROM OUTSIDE OF SAID CASING, AND ELECTRICAL TERMINAL MEANS INCLUDED IN SAID COVER PORTION AND CONNECTED TO SAID MOTOR. 